We propose to continue further studies on the possible role of cell surface lectins in cell cohesion. We are studying this problem both in cellular slime molds and in developing vertebrate muscle. In both systems we have found extractable developmentally-regulated lectins. In the slime mold systems we have clear evidence that the lectins are detectable on the surface of the cohesive cells; and that a complementary oligosaccharide receptor is also present on the surface of cohesive cells. We are engaged in further investigations of the possible role of this pair of complementary molecules in cell cohesion. In the case of developing muscle, we have purified the lectin activity by affinity chromatography and are engaged in studies of its characteristics and cellular localization. BILBIOGRAPHIC REFERENCES: Flanagan, S.D., Barondes, S.H. and Taylor, P., "Affinity Partitioning of Membranes: Cholinergic Receptor Containing Membranes from Torpedo californica." J. Biol. Chem. 251: 858-865, 1976. Barondes, S. H. and Rosen, S. D., "Cell Surface Carbohydrate-Binding Proteins May Mediate Cell Recognition." In: Neuronal Recognition, S.H. Barondes, Ed. (Plenum Press, New York), 331-356, 1976.